There have been a number of recent inventions related to the optical coupling of circuit devices to external optical signal transmission media. Some examples of these inventions will now be described. As an initial example, an integrated circuit package containing a photo-responsive semiconductor element with integral optical input coupler was developed by T. Frederiksen in U.S. Pat. No. 4,188,708, issued Feb. 19, 1980. For the next example, an optoelectronic semiconductor device with mounted optical fiber was designed by N. Inagaki in U.S. Pat. No. 4,316,204, issued Feb. 16, 1982. A low cost electro-optical connector was developed to connect an optical fiber to a plastic encapsulated electro-optical semiconductor device, by D. Stevenson in U.S. Pat. No. 4,439,006, issued Mar. 27, 1984. From these examples, it is clear that the present trend to produce optical signal processing devices to interface with an optical signal transmission medium. From this trend in circuit devices, there arises a present need for an efficient means to interconnect such optical signal elements.
The present invention relates to the optical interconnection of a plurality of individual circuit devices, or separate circuit boards, by means of a circuit board which provides the requisite electrical signal and optical signal communication linkages. This circuit board will facilitate the development of analog and digital signal processing of ever greater speed, and will provide intercommunication between the individual signal processing circuit elements of wide information bandwidths. Conventional electrical circuit connection boards alone do not have the device intercommunication capacity needed to best use modern electrical or electrical-optical devices to take advantage of their potential signal processing speed. The provision of optical channels will afford device intercommunication pathways of satisfactory bandwidth for use with such modern electrical-optical devices.
An optical data processing board was developed by R. Lindsey in U.S. Pat. No. 3,943,021, issued Mar. 9, 1976. This module structure includes a plurality of interconnected optical fibers which must be mechanically positioned for each circuit board which is to be reproduced. This method of optical circuit board fabrication is extremely labor intensive and is not easily adapted for automated manufacturing procedures. In addition to this problem, interfaces to this circuit board structure by means of several optical "windows" is not reliable due to the presence of dust and dirt, which may accumulate between the interface of an optical window and other optically conducting media. This invention does not pose an economically attractive alternative to the potential demand for optical device intercommunications on a circuit board.
A multilayer ceramic module, having optical channels fabricated therein, was developed by H. Kaiser in U.S. Pat. No. 4,169,001, issued Sept. 25, 1979. This multilayer ceramic structure is best suited for the fabrication of a hybrid microelectronic electrical-optical device, and is not well suited for the production of an entire circuit board. The manner of fabrication of such a device would make the process of the fabrication of an entire optical signal interconnection board by this method an economically prohibitive alternative. This invention will not satisfy a potential demand for optical circuit boards.
The circuit board of the present invention provides an attractive alternative to the previous inventions by its ease of fabrication by well established methods, and by its suitability to automated manufacture for economical mass production. In accordance with the present invention, previous inventions that apply to aspects of this optically conducting electronic circuit board are now presented. Specifically, the electrically conducting circuit board initially appeared in U.S. Pat. No. 2,695,351 by J. Beck et al, issued Nov. 23, 1954. The analogous structure of a monolithic optical circuit with formed optical channels appeared in U.S. Pat. No. 4,472,020 by V. Evanchuk, issued Sept. 18, 1984. This invention applies most appropriately to an individual device structure rather than to an entire device interconnection board. The ultrasonic welding of small elements having a small area of contact by use of a handheld tool appeared in U.S. Pat. No. 3,053,124 by L. Balamuth et al, issued Sept. 11, 1962. The ultrasonic welding of two adjacent optical fiber elements, for the purpose of establishing an optical signal coupling, appeared in U.S. Pat. No. 4,265,689 by C. Jeffrey, issued May 5, 1981.